1. Field of the Invention
The present invention relates to a medium discrimination device, an image forming apparatus, and a program product, and more particularly to a medium discrimination device, an image forming apparatus, and a program product for detecting a paper type and a double-feed of a medium on a conveyance route by using a simplified mechanism.
2. Discussion of the Background
A related art medium discrimination device is used in a sheet feeding unit for feeding a sheet of paper stored in a storage in a form of a plurality of overlaid sheets by sequentially separating the sheet to supply into a predetermined position. The medium discrimination device is used in, for example, a sheet feeding unit in an image forming apparatus such as a copier, a printer, a press machine, a feeding and conveyance unit in a document conveyance unit, and a document feeding and conveyance unit in a scanner. Detection of a paper type in the sheet feeding unit is performed for setting an optimum condition, since the optimum condition related to a copy condition, a print condition, a press condition, a document read condition differs depending on a type of a medium. A method of manually performing the paper type detection by an input operation performed by a user and a method of automatically performing the paper type detection by detecting a sheet are known as a method of paper type detection.
Further, detection of double feed (two or more sheets being conveyed at the same time) in the sheet feeding unit is performed for the following reason. For example, when a double-feed occurs during image formation, overlaid sheets are separated in the middle of conveyance. As a result, the separated sheet may be wound around a transfer member or a fixing member, possibly causing significant damage on a machine. Even when the overlaid sheets are discharged without being separated, a user needs to check a batch of sheets after images are formed thereon to see whether or not any double-feed has occurred, thereby causing extra work. Especially when post processing, such as stapling has been finished, more effort and time are required. To avoid the trouble, when a double-feed occurs, image forming and other processing needs to be immediately stopped and a user needs to be informed of an occurrence of the double-feed. Detection of double feed is required to control the stopping and informing. Detection by using reflected light quantity or by using transmitted light quantity is known as a method of detecting double feed.
Among the above methods, the method of detecting a paper type by the input operation performed by a user may have a problem that the user erroneously sets paper information, or incorrectly sets a sheet in a tray. When such a wrong operation occurs, a type of sheet different from the set type of sheet that the machine recognizes is used. As a result, various troubles may occur such that image quality is lowered and a sheet jam is caused due to degradation of a fixing property and an incorrect transfer condition. According to an invention proposed in the related art, the input operation performed by a user and the automatic paper type detection are used in conjunction, and, as a result, the above troubles are less likely to occur. Other technologies have also been proposed. The input operation performed by a user has been in practical use, and described in other related art. Most of the related art, however, are related to individual functional improvement in either the paper type detection or the double feed detection.